DESCRIPTION

These system calls change the owner and group of a file.
The differ only in how the file is specified:

*

chown()
changes the ownership of the file specified by
path,
which is dereferenced if it is a symbolic link.

*

fchown()
changes the ownership of the file referred to by the open file descriptor
fd.

*

lchown()
is like
chown(),
but does not dereference symbolic links.

Only a privileged process (Linux: one with the
CAP_CHOWN
capability) may change the owner of a file.
The owner of a file may change the group of the file
to any group of which that owner is a member.
A privileged process (Linux: with
CAP_CHOWN)
may change the group arbitrarily.

If the
owner
or
group
is specified as -1, then that ID is not changed.

When the owner or group of an executable file are changed by a non-superuser,
the
S_ISUID
and
S_ISGID
mode bits are cleared.
POSIX does not specify whether
this also should happen when root does the
chown();
the Linux behavior depends on the kernel version.
In case of a non-group-executable file (i.e., one for which the
S_IXGRP
bit is not set) the
S_ISGID
bit indicates mandatory locking, and is not cleared by a
chown().

RETURN VALUE

On success, zero is returned.
On error, -1 is returned, and
errno
is set appropriately.

ERRORS

Depending on the file system, other errors can be returned.
The more general errors for
chown()
are listed below.

EACCES

Search permission is denied on a component of the path prefix.
(See also
path_resolution(7).)

EFAULT

path
points outside your accessible address space.

ELOOP

Too many symbolic links were encountered in resolving
path.

ENAMETOOLONG

path
is too long.

ENOENT

The file does not exist.

ENOMEM

Insufficient kernel memory was available.

ENOTDIR

A component of the path prefix is not a directory.

EPERM

The calling process did not have the required permissions
(see above) to change owner and/or group.

EROFS

The named file resides on a read-only file system.

The general errors for
fchown()
are listed below:

EBADF

The descriptor is not valid.

EIO

A low-level I/O error occurred while modifying the inode.

ENOENT

See above.

EPERM

See above.

EROFS

See above.

CONFORMING TO

4.4BSD, SVr4, POSIX.1-2001.

The 4.4BSD version can only be
used by the superuser (that is, ordinary users cannot give away files).

NOTES

When a new file is created (by, for example,
open(2)
or
mkdir(2)),
its owner is made the same as the file system user ID of the
creating process.
The group of the file depends on a range of factors,
including the type of file system,
the options used to mount the file system,
and whether or not the set-group-ID permission bit is enabled
on the parent directory.
If the file system supports the
-o grpid
(or, synonymously
-o bsdgroups)
and
-o nogrpid
(or, synonymously
-o sysvgroups)
mount(8)
options, then the rules are as follows:

*

If the file system is mounted with
-o grpid,
then the group of a new file is made
the same as that of the parent directory.

*

If the file system is mounted with
-o nogrpid
and the set-group-ID bit is disabled on the parent directory,
then the group of a new file is made the same as the
process's file system GID.

*

If the file system is mounted with
-o nogrpid
and the set-group-ID bit is enabled on the parent directory,
then the group of a new file is made
the same as that of the parent directory.

As at Linux 2.6.25,
the
-o grpid
and
-o nogrpid
mount options are supported by ext2, ext3, ext4, and XFS.
File systems that don't support these mount options follow the
-o nogrpid
rules.

The
chown()
semantics are deliberately violated on NFS file systems
which have UID mapping enabled.
Additionally, the semantics of all system
calls which access the file contents are violated, because
chown()
may cause immediate access revocation on already open files.
Client side
caching may lead to a delay between the time where ownership have
been changed to allow access for a user and the time where the file can
actually be accessed by the user on other clients.

In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
chown()
did not follow symbolic links.
Since Linux 2.1.81,
chown()
does follow symbolic links, and there is a new system call
lchown()
that does not follow symbolic links.
Since Linux 2.1.86, this new call (that has the same semantics
as the old
chown())
has got the same syscall number, and
chown()
got the newly introduced number.

EXAMPLE

The following program changes the ownership of the file named in
its second command-line argument to the value specified in its
first command-line argument.
The new owner can be specified either as a numeric user ID,
or as a username (which is converted to a user ID by using
getpwnam(3)
to perform a lookup in the system password file).